This invention relates to planar media for high density recording and reproduction, and more particularly to devices and methods for providing low cost but high performance media and methods of fabricating the same.
As the art of recording and reproducing data from rotating media have advanced, cost performance factors have reached levels that were once thought unobtainable. By improving the media surfaces so that surface asperities are of the order of a microinch or less, by using highly efficient transducers interactive with very narrow track widths, and by aerodynamic designs which maintain the transducers at microinch or less gaps from the media surface, the number of tracks per inch and the number of bits per inch along the track have been increased by orders of magnitude, and continue to increase. At the same time, the need for mass production of the discs, head access systems and transducer devices has been met so that at this time disc drives using magnetic and magneto optical technology are commercially available that have capacities in the gigabyte range at costs which are, even for single piece quantities, in the low hundreds of dollars.
This constant refinement and improvement continues, and advances in media technology are an area of significant interest. Whereas the conventional approach has been to utilize metal and metal-based discs, i.e., aluminum, some designers have more recently utilized polymeric materials, which can be molded to shape, and then surfaced with successive layers for the desired magnetic or magneto-optical properties. These approaches have been directed toward arrangements that are in large measure, the equivalent of aluminum discs. In other words, have been designed so as to be 1:1 equivalents of metal discs, in their form factors and methods of attachment to the drive spindle. An exception is a small disc which has been molded as a single piece, integral with the central spindle, but this is a specialized version of limited general utility, because it is designed for a low cost unit of very small form factor.
The strategy of using polymeric materials for higher performance units, continues to suffer performance drawbacks. Both track registration and flyability (transducer to media spacing) are adversely affected because the media is not sufficiently stable to meet the exactness required of transducer radial position and flying height reference.
Polymeric media in accordance with the invention are configured, in relation to a central supporting drive spindle, to be integral units having an interior clamp configuration that snaps into place on the spindle and thereafter maintains concentricity during rotation, without other attachments. Further, the thickness of the media is tailored, with respect to its modulus of elasticity, to provide planar stiffness at least equal to metal-based media, assuring stability at a small sacrifice and overall height of the drive system. Furthermore, the interior clamp, which is advantageously molded integrally with the signal transduction portion of the media, can incorporate a spacer section, so as to be seated on a shoulder on the spindle mechanism, or allow stacking of discs on a common spindle. Furthermore, protruding contact elements may be integrally formed along a radial band on the disc used for a head landing area, so as to minimize stiction during starting and stopping.
In an example of an integral polymeric disc in accordance with the invention, the active recording area includes a structure of uniform thickness in which the product of the modulus of elasticity and the cube of the disc thickness provides a stiffness at least equal to that of a metal-based disc. The disc includes an interior integral clamp area in the form of a shallow conical surface having interior fingers spaced circumferentially about an interior bore sized to fit with pressure on a given spindle. The spindle has an uppermost cap member with respect to which the fingers expand as the disc is moved down into position over the cap, and then snapped into place against the outer circumference of the spindle below the cap. A circumferential band on the surface of the media encompassing the head landing area for start and stop operations includes multiple integrally molded projections to reduce stiction and minimize wear.
According to a first aspect of the invention, there is provided a rotatable device for signal recording and reproduction operations where the device has a rotatable spindle and a planar disc body. The planar disc body includes a molded member of polymeric material which has a signal transduction portion of a constant thickness. The thickness is large enough to reduce off track motion due to nonrepeatable runouts. Also included is a deformable inner radial hub coupled to an inner radial disc region of the planar body where the deformable inner radial hub has resilient members disposed about a central bore and sized to seat against the spindle circumference.
According to a second aspect of the invention, there is provided a rotatable device that has a rotatable spindle and a planar disc body. The planar disc body includes a molded member of polymeric material that has a principal signal transduction portion of constant thickness. The thickness is large enough to reduce off track motion due to non-repeatable runout. Also included is a deformable inner radial hub coupled to an inner radial disc region of the planar body.
According to a third aspect of the invention, there is provided a device for reducing frictional heating and friction between a recordable disc and a read/write head during the initiation and termination of disc rotation. The device includes a planar disc body with a plurality of protrusions in a radial band along a control bore of the disc and a read/write head wherein a pad is coupled to a contact surface of the head, interposed between the head and the central bore.